LONDON, April 25 (Reuters) - People in the European Union, who according to a United Nations body eat way more protein than necessary, could prompt big cuts in nitrogen pollution if they halved their meat and dairy consumption, a U.N.-backed report said on Friday.

Nitrogen is used in fertiliser to replace nutrients which are removed by soils during plant growth but excess nitrogen can harm the environment by polluting water, air and soil.

Nitrogen can also be released into the air by animal manure or as nitrous oxide, the third most potent greenhouse gas after carbon dioxide and methane.

Currently, 6.5 million to 8 million tonnes a year of nitrogen escape into the environment due to agricultural practices. That represents around 80 percent of nitrogen emissions from all sources, said the study by the United Nations' Economic Commission for Europe's (UNECE) Task Force on Reactive Nitrogen.

Around 79-88 percent of total emissions in the EU related to nitrogen are from livestock production. The nitrogen footprint of meat and dairy is considerably higher than that from plant-based products, the report added.

"If all people within the EU would halve their meat and dairy consumption, this would reduce greenhouse gas emissions from agriculture by 25 to 40 percent, and nitrogen emissions by 40 percent," lead author Henk Westhoek, program manager for Agriculture and Food at the Netherlands Environmental Assessment Agency, said in a statement.

On average in Europe, a person eats 83 grams of protein a day and 60 percent of this comes from animals, the study showed.

The current average per capita protein intake in the EU is about 70 percent higher than necessary, according to the World Health Organization (WHO) recommendations.

The reduction in dairy and meat consumption would also reduce the need for soy bean imports, currently used in animal feed, by 75 percent.

"The EU could become a major exporter of food products, instead of a major importer of for example soy beans," Westhoek added.

Agriculture, through meat production, is one of the main contributors to greenhouse gas emissions which are believed to fuel global warming. Estimates vary but scientists say animal agriculture could account for between 10 and 25 percent of total global emissions. (Editing by Keiron Henderson)